Divers utilize a variety of different searches for efficiently locating an underwater search object, such as a circular search which, though accurate, requires the use of an anchored line or a line held by the diver's buddy. The line is held taut, the diver swims a circle, and if the object is not found, more line is released and the diver repeats the circular search along another circle with ever-expanding circles being utilized until the search object is found. A circular search pattern is particularly useful when looking for a small item in a relatively small area, and this pattern also helps the diver maintain an accurate search in the presence of currents or surge.
Controlled searches include several patterns which are controlled by divers swimming on the surface, a guide walking on shore, or a boat motoring slowly. For most of these patterns, a team of divers work side-by-side along a rope stretched out across the bottom.
However, in lieu of such multiple-diver searches, often a single diver is required or desires to make an underwater search without assistance and might, for example, utilize a U-pattern search which neither requires a rope nor a buddy. A diver would, for example, swim an "up" leg at a predetermined number of kicks, an "across" leg at a predetermined of kicks, a "down" leg at a predetermined number of kicks (generally corresponding to the number of kicks of the "up" leg), another "across" leg, etc. The diver swims successive legs 90 degrees relative to each other to cover the bottom terrain.
A so-called expanding square pattern search is similarly effected by a diver swimming successive 90 degree related legs with progressively increasing kicks per leg with all legs being swum in either a clockwise or a counterclockwise direction. The expanding square pattern technique is particularly useful over rough bottom terrain in calm water.
Experienced divers have little difficulty in conducting such solo U-pattern, expanding square pattern or similar (triangular or "flag") patterns, but even seasoned divers at times encounter difficulties. Amateur or less experienced divers encounter difficulties in navigating such pattern searches for a variety of reasons, such as simply not trusting compass readings. A triangular or "flag" pattern requires turns of 120 degrees to remain on course, yet even seasoned divers frequently think that 60 degree turns make up a triangular dive pattern and such a mistake prevents accurate searching and places the diver far from where the diver would like to be at the completion of the search.